JP7532764B2 - Polymer Composition - Google Patents

Description

The present invention relates to a polymer composition.

Polymer compositions containing polymers such as rubber and resin and various fillers such as reinforcing agents are widely used. From the viewpoint of imparting excellent strength and the like, the use of various organic short fibers as fillers for such polymer compositions has been considered. For example, Patent Document 1 discloses a rubber composition using a master batch containing microfibrillated vegetable fibers.

However, the rubber composition of Patent Document 1 does not satisfy the specific parameters of the present application, and there is room for improvement in terms of simply imparting excellent physical properties such as viscoelasticity (E*, tan δ, etc.) and filler orientation.

JP 2013-253222 A

The present invention was made in consideration of the above-mentioned current situation, and aims to provide a polymer composition that has excellent physical properties such as viscoelasticity (E*, tan δ), durability, and impact resistance, as well as excellent orientation of microfibrillated plant fibers.

The present invention relates to a polymer composition which comprises a polymer and microfibrillated plant fibers, in which the ratio (E*a/E*b) of the complex modulus E*a (MPa) in the extrusion direction to the complex modulus E*b (MPa) in a direction perpendicular to the extrusion direction satisfies the following formula (1), and the ratio (TBa/FBa) of the breaking stress TBa (MPa) when elongated in the extrusion direction to the stress FBa (MPa) at 50% elongation of the elongation at break when elongated in the extrusion direction satisfies the following formula (2):
E*a/E*b≧1.3 (1)
TBa/FBa≧2.6 (2)

It is preferable that E*a/E*b≧1.5.

It is preferable that E*a/E*b≧2.0 be satisfied.

It is preferable that TBa/FBa≧3.0.

It is preferable that TBa/FBa≧3.4.

It is preferable that the microfibrillated plant fiber is contained in an amount of 0.5 to 30 parts by mass per 100 parts by mass of the polymer.

It is preferable that the average aspect ratio of the microfibrillated plant fibers in the polymer composition is 10 to 1000.

It is preferable that the average fiber diameter of the microfibrillated plant fibers in the polymer composition is 10 μm or less.

The present invention is a polymer composition that contains a polymer and microfibrillated plant fibers, and the ratio (E*a/E*b) of the complex modulus E*a (MPa) in the extrusion direction to the complex modulus E*b (MPa) in the direction perpendicular to the extrusion direction satisfies the above formula (1), and the ratio (TBa/FBa) of the breaking stress TBa (MPa) when elongated in the extrusion direction to the stress FBa (MPa) at 50% elongation of the breaking elongation when elongated in the extrusion direction satisfies the above formula (2). Therefore, the polymer composition has excellent physical properties such as viscoelastic properties (E*, tan δ), durability, and impact resistance, and has excellent orientation of the microfibrillated plant fibers.

[Polymer Composition]
The polymer composition of the present invention contains a polymer and microfibrillated plant fibers, and satisfies the above formulas (1) and (2). The polymer composition is excellent in physical properties such as viscoelasticity (E*, tan δ), durability, and impact resistance, and in the orientation of the microfibrillated plant fibers.

The mechanism by which such an effect is obtained is not clear, but is presumed to be as follows.
When a composition containing a polymer and microfibrillated plant fibers satisfies formula (1), it is believed that the orientation of the microfibrillated plant fibers causes anisotropy in E*, and therefore it is presumed that the orientation of the fibers in the polymer is high. Furthermore, when formula (2) is satisfied, the stress at break is 2.6 times or more higher than the stress at 50% of the elongation at break, and therefore it is presumed that the composition is resistant to impacts and vibrations in a direction perpendicular to the orientation direction. Therefore, it is presumed that the polymer composition can provide a composition that is excellent in physical properties such as viscoelastic properties (E* (rigidity), tan δ (fuel economy)) and impact resistance, and in the orientation of the microfibrillated plant fibers, and is resistant to vibrations and impacts.

The polymer composition has a ratio (E*a/E*b) of a complex elastic modulus E*a [MPa] in the extrusion direction to a complex elastic modulus E*b [MPa] in a direction perpendicular to the extrusion direction (complex elastic modulus in a direction perpendicular to the extrusion direction) that satisfies the following formula (1):
E*a/E*b≧1.3 (1)
From the viewpoints of physical properties such as viscoelastic properties (E*, tan δ), durability, and impact resistance, and the orientation of the microfibrillated plant fibers, E*a/E*b may be 1.4 or more, 1.5 or more, 1.8 or more, 2.0 or more, or 2.2 or more. There is no particular upper limit, but from the viewpoint of crack growth resistance in the extrusion direction, E*a/E*b may be 8.0 or less, 6.0 or less, or 5.0 or less.

The polymer composition has a ratio (TBa/FBa) of a breaking stress when elongated in the extrusion direction (breaking stress when elongated in the extrusion direction) TBa [MPa] to a stress when elongated in the extrusion direction by 50% of the elongation at break (stress when elongated in the extrusion direction by 50% (half of the elongation at break) of the elongation at break when elongated in the extrusion direction), which satisfies the following formula (2):
TBa/FBa≧2.6 (2)
From the viewpoints of physical properties such as viscoelastic properties (E*, tan δ), durability, and impact resistance, and the orientation of the microfibrillated plant fibers, TBa/FBa may be 3.0 or more, 3.1 or more, 3.2 or more, 3.4 or more, or 3.5 or more. There is no particular upper limit, but from the viewpoint of vibration resistance in the extrusion direction, TBa/FBa may be 8.0 or less, 6.0 or less, or 5.0 or less.

In this way, the present invention solves the problem (objective) of improving physical properties such as viscoelastic properties (E*, tan δ), durability, and impact resistance, and the orientation of microfibrillated plant fibers, by configuring a polymer composition that satisfies formulas (1) and (2) in a blend containing a polymer and microfibrillated plant fibers. In other words, the parameters of formulas (1) and (2) do not define the problem (objective), and the object of the present application is to improve physical properties such as viscoelastic properties (E*, tan δ), durability, and impact resistance, and the orientation of microfibrillated plant fibers, and a configuration that satisfies the parameters is used as a means to achieve this.

It is preferable that the polymer composition has a complex elastic modulus E*a [MPa] in the extrusion direction that satisfies the following formula (1-1).
1.0MPa≦E*a≦100MPa (1-1)
From the viewpoints of physical properties such as viscoelastic properties (E*, tan δ), durability, impact resistance, and the orientation of the microfibrillated plant fibers, the lower limit may be 1.2 MPa or more, 1.5 MPa or more, 6 MPa or more, 8 MPa or more, 10 MPa or more, or 12 MPa or more. The upper limit is not particularly limited, but from the viewpoint of impact resistance in the extrusion direction, it is more preferably 90 MPa or less, even more preferably 60 MPa or less, particularly preferably 40 MPa or less, and most preferably 20 MPa or less.

It is preferable that the polymer composition has a breaking stress TBa [MPa] when elongated in the extrusion direction that satisfies the following formula (2-1).
12MPa≦TBa≦50MPa (2-1)
From the viewpoints of physical properties such as viscoelastic properties (E*, tan δ), durability, impact resistance, and the orientation of the microfibrillated plant fibers, the lower limit may be 10 MPa or more, 15 MPa or more, 18 MPa or more, 20 MPa or more, 25 MPa or more, or 30 MPa or more. The upper limit is not particularly limited, but from the viewpoint of vibration resistance in the extrusion direction, 45 MPa or less is more preferable.

Here, as a method for satisfying formulas (1), (2), (1-1), and (2-1), there is a method for sufficiently orienting the microfibrillated plant fibers in the polymer. Specifically, there are (a) a method for mixing a dispersion liquid in which the microfibrillated plant fibers are dispersed in oil with a polymer, and (b) a method for using an organic acid amine, which may be used alone or in combination as appropriate.

Since the microfibrillated plant fiber itself is water-soluble, in order to obtain a good dispersion state in hydrophobic polymers (rubber, resin, etc.), it is generally necessary to prepare a wet masterbatch using modified microfibrillated plant fiber obtained by hydrophobizing (modifying) the microfibrillated plant fiber. In addition, a water-soluble polymer (carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), etc.) is generally used as a dispersant when producing the wet masterbatch. In contrast, for example, by mixing a dispersion in which microfibrillated plant fiber is dispersed in oil in advance using a specific dispersant (organic acid amine) with a polymer, it is possible to obtain physical properties such as viscoelastic properties (E*, tan δ), durability, impact resistance, and orientation of the microfibrillated plant fiber that are equal to or greater than those obtained when a wet masterbatch containing conventional modified microfibrillated plant fiber is used, even when unmodified microfibrillated plant fiber is used.

E*a and E*b are complex moduli measured at a temperature of 70°C and a dynamic strain of 1%, and are measured by the method described in the Examples section below. TBa and FBa are values measured at the standard test temperature (23±2°C) in accordance with JIS K6251:2017, and are measured by the method described in the Examples section below. When the polymer is rubber, E*a, E*b, TBa, and FBa are physical properties of the rubber composition after vulcanization.

The extrusion direction and the direction perpendicular to the extrusion direction are the direction in which the molding material is extruded from the extrusion port of the extrusion molding machine and the direction perpendicular to that. In the case of tires, it is desirable to set the extrusion direction as the tire circumferential direction and the direction perpendicular to the extrusion direction as the tire radial direction. The tire circumferential direction and tire radial direction are specifically the directions described in Figure 1 of JP 2009-202865 A, etc.

(polymer)
The polymer is not particularly limited, and examples thereof include known polymers such as rubber, resin, etc. These polymers may be used alone or in combination of two or more kinds.

The rubber may be any rubber commonly used in the rubber industry, including diene rubbers such as natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), styrene isoprene butadiene rubber (SIBR), ethylene propylene diene rubber (EPDM), chloroprene rubber (CR), and acrylonitrile butadiene rubber (NBR), butyl rubbers such as halogenated butyl rubber (X-IIR) and butyl rubber (IIR), and fluororubber. When applied to tires, NR, BR, SBR, etc. can be preferably used from the viewpoint of tire properties.

NR is not particularly limited, and can be any commonly used in the tire industry, such as SIR20, RSS#3, or TSR20. NR may be modified, such as modified natural rubbers such as epoxidized natural rubber (ENR), deproteinized natural rubber (DPNR), highly purified natural rubber (UPNR), hydrogenated natural rubber (HNR), and grafted natural rubber.

In the polymer composition, the content of NR in 100% by mass of the polymer is not particularly limited and may be appropriately selected depending on the application. For example, from the viewpoint of low fuel consumption, it is preferably 20% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more. The upper limit of the content is not particularly limited and may be 100% by mass.

The BR is not particularly limited, and examples thereof include those commonly used in the tire industry, such as BR with a high cis content, BR containing 1,2-syndiotactic polybutadiene crystals (SPB-containing BR), butadiene rubber synthesized using a rare earth element catalyst (rare earth BR), and tin-modified butadiene rubber modified with a tin compound (tin-modified BR). Commercially available products include those from Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, Zeon Corporation, and the like. These may be used alone or in combination of two or more types.

From the viewpoint of good flexural fatigue resistance, the cis content of BR is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more. In this specification, the cis content is a value calculated by infrared absorption spectrum analysis.

In the polymer composition, the content of BR in 100% by mass of the polymer is not particularly limited, and may be appropriately selected depending on the application. For example, from the viewpoint of low-temperature properties, it is preferably 20% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more. In addition, the upper limit of the content is not particularly limited, but is preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less.

The SBR is not particularly limited, and examples of the SBR that can be used include emulsion-polymerized styrene-butadiene rubber (E-SBR) and solution-polymerized styrene-butadiene rubber (S-SBR). Commercially available SBRs that can be used include those manufactured and sold by Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd., Dow Corporation, etc.

In the polymer composition, the content of SBR in 100% by mass of the polymer is not particularly limited, and may be appropriately selected depending on the application. For example, from the viewpoint of grip performance, it is preferably 20% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more. In addition, the upper limit of the content is not particularly limited, and may be 100% by mass.

BR and SBR may be unmodified BR and unmodified SBR, or modified BR and modified SBR. Modified BR and modified SBR may be BR and SBR having a functional group that interacts with a filler such as silica. For example, terminal-modified BR and SBR (terminal-modified BR and SBR having the above-mentioned functional group at the terminal) in which at least one terminal of BR and SBR is modified with a compound (modifier) having the above-mentioned functional group, main-chain-modified BR and SBR having the above-mentioned functional group in the main chain, main-chain terminal-modified BR and SBR having the above-mentioned functional group in the main chain and at least one terminal (for example, main-chain terminal-modified BR and SBR having the above-mentioned functional group in the main chain and modified with the above-mentioned modifier) and terminal-modified BR and SBR modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule and having a hydroxyl group or epoxy group introduced therein may be mentioned.

The functional groups include, for example, amino groups, amide groups, silyl groups, alkoxysilyl groups, isocyanate groups, imino groups, imidazole groups, urea groups, ether groups, carbonyl groups, oxycarbonyl groups, mercapto groups, sulfide groups, disulfide groups, sulfonyl groups, sulfinyl groups, thiocarbonyl groups, ammonium groups, imide groups, hydrazo groups, azo groups, diazo groups, carboxyl groups, nitrile groups, pyridyl groups, alkoxy groups, hydroxyl groups, oxy groups, and epoxy groups. These functional groups may have a substituent. Among them, from the viewpoint of tire physical properties, amino groups (preferably amino groups in which the hydrogen atoms of the amino groups are substituted with alkyl groups having 1 to 6 carbon atoms), alkoxy groups (preferably alkoxy groups having 1 to 6 carbon atoms), and alkoxysilyl groups (preferably alkoxysilyl groups having 1 to 6 carbon atoms) are preferred.

The resin is not particularly limited, and examples thereof include polyethylene (PE), polypropylene (PP), polyvinyl chloride, polystyrene, polyvinylidene chloride, fluororesins (homopolymers or copolymers of tetrachloroethylene, hexafluoropropylene, chlorotrifluoroethylene, vinylidene fluoride, vinyl fluoride, perfluoroalkyl vinyl ether, etc.), (meth)acrylic resins (homopolymers or copolymers of (meth)acrylic acid, (meth)acrylonitrile, (meth)acrylic acid esters, (meth)acrylamides, etc.), polyamide resins (nylon resins, PA), polyesters (aromatic polyesters, aliphatic polyesters, unsaturated polyesters, etc.), and the like. thermoplastic resins such as polylactic acid resin, polylactic acid and polyester copolymer resin, acrylonitrile-butadiene-styrene copolymer (ABS resin), polycarbonate (reaction product of bisphenol A or its derivatives, bisphenols, with phosgene or phenyl dicarbonate, etc.), polyphenylene oxide, (thermoplastic) polyurethane (copolymer of diisocyanates and diols, etc.), polyacetal (POM), vinyl ether resin, polysulfone resin (copolymer of 4,4'-dichlorodiphenyl sulfone and bisphenol A, etc.), cellulose resin (triacetylated cellulose, diacetylated cellulose, etc.), etc.

(Microfibrillated plant fibers)
From the viewpoints of physical properties such as viscoelastic properties (E*, tan δ), durability, and impact resistance, and the orientation and dispersibility of the microfibrillated plant fibers, the polymer composition preferably contains 0.5 to 30 parts by mass of microfibrillated plant fibers per 100 parts by mass of the polymer. The lower limit is more preferably 1 part by mass or more, even more preferably 3 parts by mass or more, and particularly preferably 4 parts by mass or more. The upper limit is more preferably 25 parts by mass or less, even more preferably 20 parts by mass or less, and particularly preferably 15 parts by mass or less.

As the microfibrillated plant fiber, cellulose microfibrils are preferred from the viewpoints of breaking strength, abrasion resistance, etc. The cellulose microfibrils are not particularly limited as long as they are derived from natural products, and examples include those derived from resource biomass such as fruits, grains, and root vegetables, wood, bamboo, hemp, jute, and kenaf, and pulp, paper, cloth, agricultural waste, waste biomass such as food waste and sewage sludge obtained using these as raw materials, unused biomass such as rice straw, wheat straw, and thinning materials, as well as cellulose produced by sea squirts, acetic acid bacteria, etc. These microfibrillated plant fibers may be used alone or in combination of two or more types.

In this specification, cellulose microfibrils typically refer to cellulose fibers with an average fiber diameter of several tens of μm (e.g., 20 to 30 μm or less), preferably 10 μm or less, and more typically refer to cellulose fibers having a microstructure with an average fiber diameter of 500 nm or less formed by an assembly of cellulose molecules (microfibrillated plant fibers with an average fiber diameter of several tens of μm or less, 10 μm or less, or 500 nm or less). Typical cellulose microfibrils can be formed, for example, as an assembly of cellulose fibers having the average fiber diameter as described above.

The method for producing microfibrillated plant fibers is not particularly limited, but examples include a method in which the raw material for cellulose microfibrils is chemically treated with an alkali such as sodium hydroxide as necessary, and then mechanically ground or beaten using a refiner, twin-screw kneader (twin-screw extruder), twin-screw kneading extruder, high-pressure homogenizer, media stirring mill, stone mill, grinder, vibration mill, sand grinder, etc. In these methods, lignin is separated from the raw material by chemical treatment, so microfibrillated plant fibers that are substantially free of lignin are obtained. Another example is a method in which the raw material for cellulose microfibrils is subjected to ultra-high pressure treatment.

Examples of microfibrillated plant fibers that can be used include products from Sugino Machine Ltd. and Daicel FineChem Ltd.

As described above, the microfibrillated plant fibers obtained by the above-mentioned manufacturing method can be sufficiently oriented in the polymer, but in addition to the unmodified microfibrillated plant fibers, it is also possible to use those that have been subjected to oxidation treatment or various chemical modification treatments, and those that have been subjected to oxidation treatment or various chemical modification treatments using natural products that can be used to produce cellulose microfibrils (e.g., wood, pulp, bamboo, hemp, jute, kenaf, agricultural waste, cloth, paper, sea squirt cellulose, etc.) as cellulose raw materials and then defibration treatment as necessary (chemically modified microfibrillated plant fibers, etc.).

Examples of chemical modification of microfibrillated plant fibers include, for example, esterification, etherification, and acetalization. Specific examples include acylation such as acetylation, cyanoethylation, amination, sulfone esterification, phosphate esterification, alkyl esterification, alkyl etherification, complex esterification, β-keto esterification, alkylation such as butylation, and chlorination. Further examples include alkyl carbamate and aryl carbamate.

The chemically modified microfibrillated plant fiber is preferably chemically modified so that the degree of substitution is within the range of 0.2 to 2.5. Here, the degree of substitution means the average number of hydroxyl groups per glucose ring unit of cellulose hydroxyl groups that have been replaced with other functional groups by chemical modification, and the theoretical maximum value is 3. The degree of substitution is more preferably within the range of 0.3 to 2.5, even more preferably within the range of 0.5 to 2.3, and particularly preferably within the range of 0.5 to 2.0. Note that when the above-mentioned chemically modified microfibrillated plant fiber is a combination of two or more types, the degree of substitution is calculated as the average for the entire chemically modified microfibrillated plant fiber.

The degree of substitution in chemically modified microfibrillated plant fibers can be confirmed, for example, by titration using 0.5N NaOH and 0.2N HCl, or by measurements such as NMR and infrared absorption spectroscopy.

A suitable example of a chemically modified microfibrillated plant fiber is an aminated microfibrillated plant fiber with a degree of substitution in the range of 0.3 to 2.5. The degree of substitution is preferably 0.3 to 2.0, more preferably 0.5 to 2.3, even more preferably 0.7 to 2.0, and particularly preferably 0.9 to 1.8.

When the chemically modified microfibrillated plant fiber is an acetylated microfibrillated plant fiber, the degree of substitution is preferably within the range of 0.3 to 2.5; when it is a sulfone esterified microfibrillated plant fiber, the degree of substitution is preferably within the range of 0.3 to 1.8; when it is an alkyl esterified microfibrillated cellulose, the degree of substitution is preferably within the range of 0.3 to 1.8; when it is a complex esterified microfibrillated cellulose, the degree of substitution is preferably within the range of 0.4 to 1.8; when it is a β-keto esterified microfibrillated cellulose, the degree of substitution is preferably within the range of 0.3 to 1.8; when it is an alkyl carbamate microfibrillated cellulose, the degree of substitution is preferably within the range of 0.3 to 1.8; and when it is an aryl carbamate microfibrillated cellulose, the degree of substitution is preferably within the range of 0.3 to 1.8.

Acetylation can be carried out, for example, by adding acetic acid, concentrated sulfuric acid, or acetic anhydride to the microfibrillated plant fiber and reacting them. Specifically, for example, the acetylation reaction can be carried out by reacting the microfibrillated plant fiber with acetic anhydride in a mixed solvent of acetic acid and toluene in the presence of a sulfuric acid catalyst, and then replacing the solvent with water, or by other conventional methods.

Amination can be carried out, for example, by performing an oxidation treatment using an N-oxyl compound such as 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), followed by reacting with an amine compound (for example, a primary amine compound having 1 to 30 carbon atoms such as oleylamine (preferably a primary amine compound having 3 to 25 carbon atoms having a saturated or unsaturated bond, more preferably a primary amine compound having 6 to 23 carbon atoms having an unsaturated bond, and even more preferably a primary amine compound having 10 to 20 carbon atoms having an unsaturated double bond)) or a quaternary alkyl ammonium salt (preferably a quaternary alkyl ammonium salt having 1 to 30 carbon atoms, more preferably a quaternary alkyl ammonium halide having 1 to 20 carbon atoms such as hexadecyltrimethylammonium chloride) in an alcohol (for example, an alcohol having 1 to 10 carbon atoms such as ethanol (preferably an alcohol having 1 to 5 carbon atoms, more preferably a primary alcohol having 1 to 4 carbon atoms)) to cause a nucleophilic substitution reaction, or by known methods such as tosyl esterification.

Sulfonation can be carried out, for example, by a simple procedure of dissolving the microfibrillated plant fiber in sulfuric acid and then pouring it into water. It can also be carried out by other methods, such as treatment with anhydrous sulfuric acid gas or treatment with chlorosulfonic acid and pyridine.

Phosphate esterification can be carried out, for example, by treating microfibrillated plant fibers that have been treated with dimethylamine or the like with phosphoric acid and urea.

Alkyl esterification can be carried out, for example, by the Schotten-Baumann method, in which microfibrillated plant fibers are reacted with a carboxylic acid chloride under basic conditions, and alkyl etherification can be carried out by the Williamson method, in which microfibrillated plant fibers are reacted with an alkyl halide under basic conditions.

Chlorination can be carried out, for example, by adding thionyl chloride in DMF (dimethylformamide) and heating.

Complex esterification can be carried out, for example, by reacting microfibrillated plant fibers with two or more types of carboxylic acid anhydrides or carboxylic acid chlorides under basic conditions.

β-Ketoesterification can be carried out, for example, by reacting microfibrillated plant fibers with diketene or alkyl ketene dimer, or by transesterification of microfibrillated plant fibers with β-ketoester compounds such as alkyl acetoacetates.

Alkyl carbamate formation can be carried out, for example, by reacting microfibrillated plant fibers with an alkyl isocyanate in the presence of a basic catalyst or a tin catalyst.

Aryl carbamate formation can be carried out, for example, by reacting microfibrillated plant fibers with aryl isocyanate in the presence of a basic catalyst or a tin catalyst.

The average fiber diameter of the microfibrillated plant fibers in the polymer composition is preferably 10 μm or less from the viewpoints of physical properties such as viscoelastic properties (E*, tan δ), durability, and impact resistance, and the orientation and dispersibility of the microfibrillated plant fibers. The average fiber diameter is more preferably 500 nm or less, even more preferably 200 nm or less, particularly preferably 100 nm or less, and most preferably 50 nm or less. There is no particular lower limit to the average fiber diameter, but because the microfibrillated plant fibers are difficult to disentangle and disperse, it is preferably 3 nm or more, more preferably 4 nm or more, even more preferably 10 nm or more, and particularly preferably 20 nm or more.

The average fiber length of the microfibrillated plant fibers in the polymer composition is preferably 100 nm or more, more preferably 300 nm or more, and even more preferably 500 nm or more. The upper limit is not particularly limited, but is preferably 5 mm or less, more preferably 50 μm or less, even more preferably 20 μm or less, particularly preferably 10 μm or less, and most preferably 5 μm or less. When the average fiber length is less than the lower limit or exceeds the upper limit, the same tendency as the average fiber diameter described above is observed.

When the microfibrillated plant fiber is a combination of two or more types, the average fiber diameter and average fiber length are calculated as the average for the entire microfibrillated plant fiber.

From the viewpoints of physical properties such as viscoelastic properties (E*, tan δ), durability, and impact resistance, and the orientation and dispersibility of the microfibrillated plant fibers, the average aspect ratio of the microfibrillated plant fibers in the polymer composition is preferably 10 to 1000. The lower limit is preferably 50 or more, and more preferably 100 or more. The upper limit is preferably 1000 or less, more preferably 900 or less, and even more preferably 800 or less.
The average aspect ratio can be calculated by the following formula.
Average aspect ratio = average fiber length/average fiber diameter

In this specification, the average fiber diameter and average fiber length of microfibrillated plant fibers can be measured by image analysis using scanning electron microscopy, image analysis using transmission electron microscopy, image analysis using atomic force microscopy, analysis of X-ray scattering data, pore electrical resistance method (Coulter principle method), etc.

The polymer composition containing a polymer and microfibrillated plant fibers and satisfying the formulas (1) and (2) can be produced, for example, by a production method including step 1 of preparing a mixed liquid containing microfibrillated plant fibers, oil, and an organic acid amine, and step 2 of producing a polymer composition containing the mixed liquid and a polymer. As long as the production method includes the above steps, it may also include other steps, and each of the above steps may be performed once or repeatedly multiple times.

In step 1, a mixed liquid containing microfibrillated plant fibers, oil, and an organic acid amine is prepared by sequentially dropping or injecting these, or by mixing the microfibrillated plant fibers, oil, and organic acid amine and then dispersing them by a known method using, for example, a high-speed homogenizer, an ultrasonic homogenizer, a colloid mill, a blender mill, or the like. The temperature and time during preparation can be appropriately set within the range normally used so that the microfibrillated plant fibers are sufficiently dispersed in the oil, or can be appropriately adjusted while measuring the viscosity of the mixed liquid so that it has the desired viscosity.

In the above mixture, from the viewpoints of physical properties such as viscoelastic properties (E*, tan δ), durability, and impact resistance, and the orientation and dispersibility of the microfibrillated plant fibers, the mixture ratio of oil to microfibrillated plant fibers (solid content) [oil amount (parts by mass)/microfibrillated plant fiber amount (parts by mass)] is preferably 10/90 to 90/10, more preferably 20/80 to 80/20, even more preferably 30/70 to 70/30, and particularly preferably 40/60 to 60/40.

In the above mixture, from the viewpoint of physical properties such as viscoelastic properties (E*, tan δ), durability, and impact resistance, and the orientation and dispersibility of the microfibrillated plant fiber, the amount of organic acid amine per 100 parts by mass (solid content) of microfibrillated plant fiber is preferably within the range of 0.1 to 50 parts by mass. The lower limit is more preferably 5 parts by mass or more, and even more preferably 10 parts by mass or more. The upper limit is more preferably 30 parts by mass or less, even more preferably 25 parts by mass or less, and particularly preferably 20 parts by mass or less.

(oil)
The oil is not particularly limited, and examples thereof include known oils such as process oil, vegetable oil, or mixtures thereof. Examples of process oils include paraffin-based process oil, aromatic process oil, naphthene-based process oil, low PCA (polycyclic aromatic) process oil such as TDAE and MES. Examples of vegetable oils include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice oil, safflower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, and tung oil. These may be used alone or in combination of two or more.

From the viewpoint of LCA (Life Cycle Assessment), it is preferable to use plant-derived glycerol fatty acid triester (vegetable oil) as the oil. Here, glycerol fatty acid triester is an ester of fatty acid and glycerin, and is also called triglyceride or tri-O-acylglycerin.

The fatty acids constituting plant-derived glycerol fatty acid triesters are known to be mainly palmitic acid (16 carbon atoms, 0 unsaturated bonds), stearic acid (18 carbon atoms, 0 unsaturated bonds), oleic acid (18 carbon atoms, 1 unsaturated bond), and linoleic acid (18 carbon atoms, 2 unsaturated bonds), and the total content of palmitic acid, stearic acid, oleic acid, and linoleic acid in 100% by mass of the constituent fatty acids is usually 80% by mass or more, preferably 90% by mass or more.

The glycerol fatty acid triester preferably has a saturated fatty acid content of 10 to 25% by mass out of 100% by mass of the constituent fatty acids. The lower limit is more preferably 12% by mass or more, and the upper limit is more preferably 20% by mass or less, even more preferably 18% by mass or less, and particularly preferably 15% by mass or less.

The glycerol fatty acid triester preferably has a content of monounsaturated fatty acids having one unsaturated bond in 100% by mass of constituent fatty acids of less than 50% by mass, more preferably 45% by mass or less, even more preferably 40% by mass or less, particularly preferably 35% by mass or less, and most preferably 30% by mass or less. There is no particular lower limit, but it is preferably 8% by mass or more, more preferably 14% by mass or more, and even more preferably 20% by mass or more.

The glycerol fatty acid triester preferably contains polyunsaturated fatty acids having two or more unsaturated bonds in 100% by mass of the constituent fatty acids, and more preferably contains 50% by mass or more, more preferably 55% by mass or more, and even more preferably 60% by mass or more. There is no particular upper limit, but it is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less.

The content of diunsaturated fatty acids having two unsaturated bonds in 100% by mass of the constituent fatty acids of the glycerol fatty acid triester is preferably 35 to 80% by mass, more preferably 40 to 70% by mass, and even more preferably 45 to 65% by mass. In addition, the content of triunsaturated fatty acids having three unsaturated bonds in 100% by mass of the constituent fatty acids is preferably 3 to 25% by mass, and more preferably 5 to 15% by mass.

The total content of unsaturated fatty acids in the glycerol fatty acid triester is preferably 75 to 90% by mass, more preferably 80 to 88% by mass, even more preferably 82 to 88% by mass, and particularly preferably 85 to 88% by mass, based on 100% by mass of the constituent fatty acids.

It is preferable that the glycerol fatty acid triester satisfies the following formula (A).
The lower limit of the following formula (A) is preferably 100 or more, more preferably 120 or more, even more preferably 140 or more, and particularly preferably 150 or more, and the upper limit is preferably 190 or less, more preferably 180 or less, and even more preferably 170 or less.
80≦content (mass%) of monounsaturated fatty acids having one unsaturated bond in 100% by mass of constituent fatty acids×1 (number of unsaturated bonds)+content (mass%) of diunsaturated fatty acids having two unsaturated bonds in 100% by mass of constituent fatty acids×2 (number of unsaturated bonds)+content (mass%) of triunsaturated fatty acids having three unsaturated bonds in 100% by mass of constituent fatty acids×3 (number of unsaturated bonds)≦200 Formula (A)

When the glycerol fatty acid triester is derived from a plant, the unsaturated bond in the constituent fatty acid is usually a double bond.

The glycerol fatty acid triester preferably has an average carbon number of 15 to 21, more preferably 16 to 20, and even more preferably 17 to 19, of constituent fatty acids.
In this specification, the average carbon number of the constituent fatty acids is calculated by the following formula (D).
Average carbon number of constituent fatty acids=ΣContent (mass%) of fatty acids having carbon number n in 100 mass% of constituent fatty acids×n (carbon number)/100 Formula (D)

The glycerol fatty acid triester is preferably liquid at room temperature (25° C.). The melting point of the glycerol fatty acid triester is preferably 20° C. or lower, more preferably 17° C. or lower, even more preferably 0° C. or lower, and particularly preferably −5° C. or lower.
The lower limit is not particularly limited, but is preferably −100° C. or higher, and more preferably −90° C. or higher.
The melting point of the glycerol fatty acid triester can be measured by differential scanning calorimetry (DSC).

The iodine value of the glycerol fatty acid triester is preferably 60 or more, more preferably 70 or more, even more preferably 80 or more, particularly preferably 100 or more, and most preferably 120 or more. The iodine value is preferably 160 or less, more preferably 150 or less, and even more preferably 135 or less.
In this specification, the iodine value is the amount of halogen bonded when 100 g of a glycerol fatty acid triester is reacted with a halogen, and is converted into the number of grams of iodine, and is a value measured by potentiometric titration (JIS K0070).

Examples of plant-derived glycerol fatty acid triesters include those derived from soybean oil, sesame oil, rice oil, safflower oil, corn oil, olive oil, rapeseed oil, etc. Among these, soybean oil, sesame oil, rice oil, and rapeseed oil are preferred, soybean oil, sesame oil, and rice oil are more preferred, and soybean oil is even more preferred, because they are inexpensive, available in large quantities, and have a high performance-improving effect.

The above fatty acid composition can be measured by GLC (gas-liquid chromatography).

As the oil, a product obtained by saponifying a plant-derived glycerol fatty acid triester (vegetable oil) (saponified vegetable oil) can also be suitably used. The saponification can be carried out by adding an alkali to the vegetable oil and leaving it to stand at a predetermined temperature for a certain period of time. Stirring, etc. may be carried out as necessary.

Alkalis that can be used in the saponification treatment include sodium hydroxide, potassium hydroxide, calcium hydroxide, amine compounds, etc., and from the viewpoint of the effectiveness of the saponification treatment, it is particularly preferable to use sodium hydroxide or potassium hydroxide.

The amount of alkali added is not particularly limited, but for example, the lower limit is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and even more preferably 1 part by mass or more, relative to 100 parts by mass of vegetable oil. The upper limit is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less.

The temperature of the saponification treatment can be set appropriately within a range in which the saponification reaction by alkali can proceed at a sufficient reaction rate and in a range in which the vegetable oil does not deteriorate, but is usually preferably 20 to 70°C, more preferably 30 to 70°C. In addition, when the vegetable oil is left to stand for treatment, the treatment time depends on the treatment temperature, but taking into consideration both sufficient treatment and improved productivity, it is preferably 30 minutes to 48 hours, more preferably 1 to 24 hours.

Commercially available oils, glycerol fatty acid triesters, etc. include products from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., Japan Energy Co., Ltd., Orisoy Co., Ltd., H&R Corporation, Toyokuni Oil Mills Co., Ltd., Showa Shell Sekiyu K.K., Fuji Kosan Co., Ltd., Nisshin Oillio Co., Ltd., J-Oil Mills Co., Ltd., Showa Sangyo Co., Ltd., Fuji Oil Co., Ltd., Miyoshi Oil Co., Ltd., and Boso Oil Co., Ltd., etc.

In addition, from the viewpoint of physical properties such as viscoelastic properties (E*, tan δ), durability, and impact resistance, and the orientation and dispersibility of the microfibrillated plant fibers, the resulting polymer composition preferably contains 0.5 to 30 parts by mass of oil per 100 parts by mass of polymer. The lower limit is more preferably 1 part by mass or more, even more preferably 3 parts by mass or more, and particularly preferably 4 parts by mass or more. The upper limit is more preferably 25 parts by mass or less, even more preferably 20 parts by mass or less, and particularly preferably 15 parts by mass or less.

(Organic acid amine)
By adding an organic acid amine to the microfibrillated plant fibers and oil, the hydrophilic side of the organic acid amine becomes compatible with the microfibrillated plant fibers, and the hydrophobic side becomes compatible with the oil. Then, when this mixture is blended with a polymer such as rubber or resin, the oil disperses in the polymer and the microfibrillated plant fibers are dispersed and oriented, improving the physical properties and orientation of the composition, since the oil used does not affect the polymer.

An organic acid amine (organic acid amine salt) is composed of an organic acid and an amine. Examples of amines constituting an organic acid amine include primary amines or secondary amines containing one or two hydrogen atoms bonded to a nitrogen atom. The amine may be either a monoamine or a polyamine. The number of carbon atoms in the amine (amine compound) is preferably 1 to 24.

Examples of amines include methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, heptylamine, octylamine, nonylamine, decylamine, undecylamine, dodecylamine, tridecylamine, tetradecylamine, pentadecylamine, hexadecylamine, heptadecylamine, octadecylamine, cyclopentylamine, cyclohexylamine, and cycloheptylamine. Alkylene diamines can also be used as amines, and specific examples include methylene diamine, ethylene diamine, propylene diamine, butylene diamine, pentylene diamine, and hexamethylene diamine. Polyalkylene polyamines can also be used, and specific examples include diethylene triamine, triethylene tetramine, tetraethylene pentamine, pentaethylene hexamine, dipropylene triamine, dibutylene triamine, tributylene tetramine, and tetrapropylene pentamine.

The organic acids constituting the organic acid amines include aliphatic carboxylic acids, alicyclic carboxylic acids, aromatic carboxylic acids, etc. These carboxylic acids may be monocarboxylic acids, dicarboxylic acids, other polycarboxylic acids, etc., and may be either saturated or unsaturated carboxylic acids. Other examples of organic acids include aliphatic sulfonic acids, aromatic sulfonic acids, alkyl salicylic acids, and alkylphenol compounds.

As the aliphatic carboxylic acid, monocarboxylic acids, dicarboxylic acids, etc. are suitable. The number of carbon atoms is preferably 4 to 30, more preferably 6 to 24. Specifically, alkanoic acids such as hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, octadecanoic acid, nonadecanoic acid, eicosanoic acid, docosanoic acid (behenic acid), and branched alkanoic acids thereof (2-methylpentanoic acid, 2-ethylhexanoic acid, 4-propylpentanoic acid, 2-methyldecanoic acid, 3-methylhendecanoic acid, 2-methyldodecanoic acid, 2-methyltridecanoic acid, 2-methyltetradecanoic acid, 2-ethyltetradecanoic acid, 2- propyldecanoic acid, 2-ethylhexadecanoic acid, 2-methyloctadecanoic acid); hexenoic acid, octenoic acid, decenoic acid, dodecenoic acid, tetradecenoic acid, hexadecenoic acid, octadecenoic acid, eicosenoic acid, docosenoic acid, octadecatrienylic acid, hexanedioic acid, heptanedioic acid, octanedioic acid, nonanedioic acid, decanedioic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, heptadecanedioic acid, octadecanedioic acid, nonadecanedioic acid, eicosane diacid, docosane diacid, and other dicarboxylic acids can be mentioned.

Examples of alicyclic carboxylic acids include cyclohexane monocarboxylic acid and cyclohexane dicarboxylic acid.

As the aromatic carboxylic acid, in addition to a carboxylic acid having a carboxyl group directly bonded to an aromatic ring, a carboxylic acid having a carboxyl group on a side chain can be used. The aromatic hydrocarbon group in the aromatic carboxylic acid may be either a single ring or a polycyclic condensed ring, and examples thereof include benzene, naphthalene, anthracene, phenanthrene, indene, fluorene, and biphenyl. As the aromatic carboxylic acid, a monocarboxylic acid, a dicarboxylic acid, or other polycarboxylic acid can be used. Specific examples of aromatic carboxylic acids include benzoic acid, phthalic acid, phenylacetic acid, mandelic acid, and derivatives thereof.

Aliphatic sulfonic acids and aromatic sulfonic acids are compounds consisting of an aliphatic or aromatic hydrocarbon group and a sulfonic acid group, and are represented by RSO ₃ H and (R') _n ArSO ₃ H, respectively. R and R' each represent an aliphatic hydrocarbon group, and Ar represents an aromatic hydrocarbon group. The aliphatic sulfonic acid may be one having a chain hydrocarbon group having 4 to 40 carbon atoms. The aromatic sulfonic acid may be one substituted with one or more chain hydrocarbon groups. The chain hydrocarbon group is preferably an alkyl group having 4 to 40 carbon atoms (particularly an alkyl group having 12 or more carbon atoms), and specific examples thereof include a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, an octadecyl group, a nonadecyl group, an eicosyl group, a tetraxyl group, a pentacosyl group, a hexacosyl group, a heptadecyl group, an octacosyl group, a nonacosyl group, a triacontyl group, a pentatriacontyl group, an octatriacontyl group, etc. As with the aromatic carboxylic acid, the aromatic hydrocarbon group may be either a monocyclic or a polycyclic condensed ring, and similarly, examples thereof include benzene, naphthalene, etc.

In addition, from the viewpoint of physical properties such as viscoelastic properties (E*, tan δ), durability, and impact resistance, and the orientation and dispersibility of the microfibrillated plant fibers, the resulting polymer composition preferably contains 0.1 to 50 parts by mass of organic acid amine per 100 parts by mass of the microfibrillated plant fibers. The lower limit is more preferably 0.1 parts by mass or more, even more preferably 10 parts by mass or more, and particularly preferably 15 parts by mass or more. The upper limit is more preferably 50 parts by mass or less, even more preferably 45 parts by mass or less, and particularly preferably 40 parts by mass or less.

In the preparation of the mixed solution containing the microfibrillated plant fiber, oil, and organic acid amine in step 1, the microfibrillated plant fiber may be mixed with the oil and organic acid amine in the state of an aqueous solution (aqueous solution of microfibrillated plant fiber) in which the microfibrillated plant fiber is dispersed in water, or the aqueous solution of microfibrillated plant fiber may be mixed with the oil and organic acid amine after solvent replacement with ethanol or the like, or the microfibrillated plant fiber may be mixed with the oil and organic acid amine as it is. Note that when the aqueous solution of microfibrillated plant fiber is mixed with the oil and organic acid amine, a strong acid such as hydrochloric acid or sulfuric acid may then be added as necessary, and the mixture may be heated (for example, at 120 to 200°C, preferably 140 to 180°C) to remove water by azeotropy, etc.

The aqueous solution of microfibrillated plant fibers can be produced by known methods, for example, by dispersing microfibrillated plant fibers in water using a high-speed homogenizer, ultrasonic homogenizer, colloid mill, blender mill, etc. The temperature and time during preparation can also be appropriately set so that the microfibrillated plant fibers are sufficiently dispersed in water.

The content (solids content) of microfibrillated plant fibers in the aqueous solution of microfibrillated plant fibers is preferably 0.2 to 20% by mass, more preferably 0.5 to 10% by mass, and even more preferably 0.5 to 3% by mass.

In step 2, a polymer composition containing the mixed liquid obtained in step 1 and a polymer is prepared by mixing at least the mixed liquid and the polymer. The mixed liquid may be mixed with a polymer or the like after adding a strong acid such as hydrochloric acid or sulfuric acid, heating (for example, 120 to 200°C, preferably 140 to 180°C), and removing moisture by azeotropy, if necessary. The mixing may be performed by a known mixing method, for example, a method of kneading each component using a rubber kneading device such as an open roll or a Banbury mixer, or a method of kneading each component using an extruder (such as a twin-screw extruder). The polymer composition described above can be prepared by mixing the mixed liquid containing microfibrillated plant fibers, oil, etc., the polymer, and other components as necessary.

(Other ingredients)
The polymer composition may contain fillers other than the microfibrillated vegetable fibers. Examples of the fillers include carbon black, silica, calcium carbonate, talc, alumina, clay, aluminum hydroxide, aluminum oxide, and mica. When the polymer composition is applied to tires, carbon black and silica are preferred.

The carbon black is not particularly limited, but examples thereof include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. Commercially available products include those from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shin-Nichika Carbon Co., Ltd., Columbia Carbon Co., Ltd., and the like. These may be used alone or in combination of two or more types.

When carbon black is included, its content is preferably 5 parts by mass or more, more preferably 15 parts by mass or more, per 100 parts by mass of the polymer. By making it equal to or more than the lower limit, good abrasion resistance, grip performance, etc. tend to be obtained. In addition, the above content is preferably 100 parts by mass or less, more preferably 50 parts by mass or less. By making it equal to or less than the upper limit, good processability of the polymer composition tends to be obtained.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 10 m ² /g or more, more preferably 30 m ² /g or more, and even more preferably 35 m ² /g or more. By making it equal to or more than the lower limit, good wear resistance and grip performance tend to be obtained. In addition, the N ₂ SA is preferably 200 m ² /g or less, more preferably 150 m ² /g or less, and even more preferably 130 m ² /g or less. By making it equal to or less than the upper limit, good dispersion of carbon black tends to be obtained.
The nitrogen adsorption specific surface area of carbon black is determined in accordance with JIS K6217-2:2001.

Examples of silica include dry process silica (anhydrous silica) and wet process silica (hydrated silica). Of these, wet process silica is preferred because it has a large number of silanol groups. Commercially available products include those from Degussa, Rhodia, Tosoh Silica, Solvay Japan, and Tokuyama. These may be used alone or in combination of two or more.

When silica is included, its content is preferably 25 parts by mass or more, more preferably 30 parts by mass or more, and even more preferably 50 parts by mass or more, relative to 100 parts by mass of the polymer. By making it equal to or more than the lower limit, good wet grip performance and handling stability tend to be obtained. There is no particular limit to the upper limit of the content, but it is preferably 300 parts by mass or less, more preferably 200 parts by mass or less, even more preferably 170 parts by mass or less, particularly preferably 100 parts by mass or less, and most preferably 80 parts by mass or less. By making it equal to or less than the upper limit, good dispersibility tends to be obtained.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 70 m ² /g or more, more preferably 140 m ² /g or more, and even more preferably 160 m ² /g or more. By making it equal to or more than the lower limit, good wet grip performance and breaking strength tend to be obtained. In addition, the upper limit of the N ₂ SA of silica is not particularly limited, but is preferably 500 m ² /g or less, more preferably 300 m ² /g or less, and even more preferably 250 m ² /g or less. By making it equal to or less than the upper limit, good dispersibility tends to be obtained.
The N ₂ SA of silica is a value measured by the BET method in accordance with ASTM D3037-93.

When the polymer composition contains silica, it preferably further contains a silane coupling agent.
The silane coupling agent is not particularly limited, and examples thereof include bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(2-triethoxysilylethyl)trisulfide, bis(4-trimethoxysilylbutyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)disulfide, bis(4-triethoxysilylbutyl)disulfide, bis(3-trimethoxysilylpropyl)disulfide, bis(2-trimethoxysilylethyl)disulfide, bis(4-trimethoxysilylbutyl)disulfide, bis(3-trimethoxysilylpropyl)disulfide, bis(2-trimethoxysilylethyl)disulfide, bis(4-trimethoxysilylbutyl)disulfide, 3-trimethoxysilylpropyl-N,N-dimethylthiocalcium. Examples of such silanes include sulfide-based silanes such as bamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, and 3-triethoxysilylpropyl methacrylate monosulfide; mercapto-based silanes such as 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and Momentive's NXT and NXT-Z; vinyl-based silanes such as vinyltriethoxysilane and vinyltrimethoxysilane; amino-based silanes such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; glycidoxy-based silanes such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based silanes such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro-based silanes such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. As commercially available products, products of Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., Dow Corning Toray Co., Ltd., etc. can be used. These may be used alone or in combination of two or more kinds.

The content of the silane coupling agent is preferably 3 parts by mass or more, and more preferably 6 parts by mass or more, relative to 100 parts by mass of silica. When it is 3 parts by mass or more, good breaking strength and the like tend to be obtained. Furthermore, the content is preferably 20 parts by mass or less, and more preferably 15 parts by mass or less. When it is 20 parts by mass or less, an effect commensurate with the amount blended tends to be obtained.

The polymer composition may contain a solid resin (a polymer that is in a solid state at room temperature (25°C)).

When a solid resin is contained, the content is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of the polymer. The content is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 20 parts by mass or less. If it is within the above range, good wet grip performance tends to be obtained.

The solid resin is not particularly limited, but examples thereof include solid styrene-based resins, coumarone-indene resins, terpene-based resins, p-t-butylphenol acetylene resins, acrylic resins, dicyclopentadiene-based resins (DCPD-based resins), C5-based petroleum resins, C9-based petroleum resins, and C5C9-based petroleum resins. These may be used alone or in combination of two or more.

Solid styrene-based resins are solid polymers that use styrene-based monomers as constituent monomers, and examples of such resins include polymers in which styrene-based monomers are polymerized as the main component (50% by mass or more). Specific examples include homopolymers in which styrene-based monomers (styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, etc.) are polymerized alone, copolymers in which two or more styrene-based monomers are copolymerized, and copolymers of styrene-based monomers and other monomers that can be copolymerized with them.

Examples of the other monomers include acrylonitriles such as acrylonitrile and methacrylonitrile, unsaturated carboxylic acids such as acrylics and methacrylic acid, unsaturated carboxylic acid esters such as methyl acrylate and methyl methacrylate, dienes such as chloroprene and butadiene isoprene, olefins such as 1-butene and 1-pentene, α,β-unsaturated carboxylic acids such as maleic anhydride or their acid anhydrides, etc.

Among these, solid α-methylstyrene resins (α-methylstyrene homopolymers, copolymers of α-methylstyrene and styrene, etc.) are preferred.

Solid coumarone-indene resin is a resin that contains coumarone and indene as the main monomer components that make up the resin skeleton (main chain), and monomer components that may be contained in the skeleton other than coumarone and indene include styrene, α-methylstyrene, methylindene, vinyltoluene, etc.

Examples of solid terpene resins include polyterpene, terpene phenol, and aromatic modified terpene resins.
Polyterpenes are resins obtained by polymerizing terpene compounds and their hydrogenated products. Terpene compounds are hydrocarbons represented by the formula (C ₅ H ₈ ) _n and their oxygen-containing derivatives, and are compounds having a basic skeleton of a terpene classified into monoterpene (C ₁₀ H ₁₆ ), sesquiterpene (C ₁₅ H ₂₄ ), diterpene (C ₂₀ H ₃₂ ), etc. Examples of such compounds include α-pinene, β-pinene, dipentene, limonene, myrcene, alloocimene, ocimene, α-phellandrene, α-terpinene, γ-terpinene, terpinolene, 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol, and γ-terpineol.

Solid polyterpenes include terpene resins such as α-pinene resin, β-pinene resin, limonene resin, dipentene resin, and β-pinene/limonene resin, which are made from the above-mentioned terpene compounds, as well as solid resins such as hydrogenated terpene resins, which are made by hydrogenating the terpene resins.

The solid terpene phenols include solid resins obtained by copolymerizing the above-mentioned terpene compounds with phenolic compounds, and solid resins obtained by hydrogenating the above-mentioned resins. Specifically, the solid resins include solid resins obtained by condensing the above-mentioned terpene compounds, phenolic compounds, and formalin. Examples of phenolic compounds include phenol, bisphenol A, cresol, and xylenol.

The solid aromatic modified terpene resin includes a solid resin obtained by modifying a terpene resin with an aromatic compound, and a solid resin obtained by hydrogenating the resin. The aromatic compound is not particularly limited as long as it is a compound having an aromatic ring, and examples thereof include phenolic compounds such as phenol, alkylphenol, alkoxyphenol, and unsaturated hydrocarbon group-containing phenol; naphthol compounds such as naphthol, alkylnaphthol, alkoxynaphthol, and unsaturated hydrocarbon group-containing naphthol; styrene derivatives such as styrene, alkylstyrene, alkoxystyrene, and unsaturated hydrocarbon group-containing styrene; coumarone, indene, etc.

An example of a solid p-t-butylphenol acetylene resin is a solid resin obtained by a condensation reaction between p-t-butylphenol and acetylene.

The solid acrylic resin is not particularly limited, but a solvent-free solid acrylic resin is preferably used because it has few impurities and produces a resin with a sharp molecular weight distribution.

Solid solventless acrylic resins include (meth)acrylic resins (polymers) synthesized by high-temperature continuous polymerization (high-temperature continuous bulk polymerization) (methods described in U.S. Pat. No. 4,414,370, JP-A-59-6207, JP-B-5-58005, JP-A-1-313522, U.S. Pat. No. 5,010,166, Toa Gosei Kenkyuu Nenpo TREND 2000 Vol. 3, pp. 42-45, etc.) with minimal use of secondary raw materials such as polymerization initiators, chain transfer agents, and organic solvents. In this specification, (meth)acrylic means methacryl and acrylic.

The solid acrylic resin preferably does not substantially contain auxiliary materials such as a polymerization initiator, a chain transfer agent, or an organic solvent. In addition, the acrylic resin is preferably one that has a relatively narrow composition distribution and molecular weight distribution obtained by continuous polymerization.

As described above, the solid acrylic resin is preferably one that does not substantially contain auxiliary raw materials such as polymerization initiators, chain transfer agents, and organic solvents, i.e., one that has high purity. The purity of the solid acrylic resin (the proportion of resin contained in the resin) is preferably 95% by mass or more, more preferably 97% by mass or more.

Examples of monomer components constituting solid acrylic resins include (meth)acrylic acid, (meth)acrylic acid esters (alkyl esters, aryl esters, aralkyl esters, etc.), (meth)acrylamide, and (meth)acrylic acid derivatives such as (meth)acrylamide derivatives.

In addition, aromatic vinyls such as styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, divinylbenzene, trivinylbenzene, and divinylnaphthalene may be used together with (meth)acrylic acid or (meth)acrylic acid derivatives as monomer components constituting solid acrylic resins.

The solid acrylic resin may be a resin composed only of a (meth)acrylic component, or a resin containing components other than the (meth)acrylic component as constituent elements.
The solid acrylic resin may have a hydroxyl group, a carboxyl group, a silanol group, or the like.

As solid resins, for example, products from Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical Company, Nitto Chemical Co., Ltd., Nippon Shokubai Co., Ltd., JXTG Nippon Oil & Energy Corporation, Arakawa Chemical Industries Co., Ltd., Taoka Chemical Co., Ltd., etc. can be used.

The polymer composition preferably contains an antioxidant from the viewpoints of crack resistance, ozone resistance, etc.

The anti-aging agent is not particularly limited, but may be naphthylamine-based anti-aging agents such as phenyl-α-naphthylamine; diphenylamine-based anti-aging agents such as octylated diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylene Examples of such antioxidants include p-phenylenediamine antioxidants such as diamines; quinoline antioxidants such as polymerized 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol antioxidants such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; and bis, tris, and polyphenol antioxidants such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane. Among these, p-phenylenediamine antioxidants and quinoline antioxidants are preferred, and N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine and polymerized 2,2,4-trimethyl-1,2-dihydroquinoline are more preferred. Commercially available products include those manufactured by Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Co., Ltd., and Flexis Co., Ltd.

The content of the antioxidant is preferably 0.2 parts by mass or more, more preferably 0.5 parts by mass or more, per 100 parts by mass of the polymer. By making the content equal to or more than the lower limit, sufficient ozone resistance tends to be obtained. The content is preferably 7.0 parts by mass or less, more preferably 4.0 parts by mass or less. By making the content equal to or less than the upper limit, a good appearance tends to be obtained.

The polymer composition preferably contains stearic acid. From the viewpoint of the above-mentioned balance of performance, the content of stearic acid is preferably 0.5 to 10 parts by mass or more, more preferably 0.5 to 5 parts by mass, per 100 parts by mass of the polymer.

The stearic acid used can be any known product, such as products from NOF Corp., NOF Corporation, Kao Corp., Fujifilm Wako Pure Chemical Industries, Ltd., Chiba Fatty Acid Co., Ltd., etc.

The polymer composition preferably contains zinc oxide. From the viewpoint of the above-mentioned performance balance, the content of zinc oxide is preferably 0.5 to 10 parts by mass, more preferably 1 to 5 parts by mass, per 100 parts by mass of the polymer.

As zinc oxide, conventionally known products can be used, such as products from Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc.

The polymer composition may contain a wax. The wax is not particularly limited, and examples thereof include petroleum-based waxes and natural waxes. Synthetic waxes obtained by refining or chemically treating multiple waxes may also be used. These waxes may be used alone or in combination of two or more types.

Petroleum-based waxes include paraffin wax and microcrystalline wax. Natural waxes are not particularly limited as long as they are derived from resources other than petroleum, and examples include vegetable waxes such as candelilla wax, carnauba wax, Japan wax, rice wax, and jojoba wax; animal waxes such as beeswax, lanolin, and spermaceti; mineral waxes such as ozokerite, ceresin, and petrolactam; and refined products thereof. Commercially available products include, for example, products from Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., and Seiko Chemical Co., Ltd. The wax content may be appropriately set in terms of ozone resistance and cost.

When the polymer composition is a rubber composition, it is preferable to add sulfur, as this forms an appropriate amount of crosslinked chains in the polymer chains and imparts good rubber properties.

The sulfur content is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 0.7 parts by mass or more, per 100 parts by mass of the polymer. The content is preferably 6.0 parts by mass or less, more preferably 4.0 parts by mass or less, and even more preferably 3.0 parts by mass or less. By keeping the content within the above range, a good balance of the above-mentioned performances tends to be obtained.

Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, and soluble sulfur, which are commonly used in the rubber industry. Commercially available products include those from Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemical Industry Co., Ltd., Flexis Corporation, Nippon Kanzuri Kogyo Co., Ltd., and Hosoi Chemical Industry Co., Ltd. These may be used alone or in combination of two or more types.

When the polymer composition is a rubber composition, it preferably contains a vulcanization accelerator.
The content of the vulcanization accelerator is not particularly limited and may be freely determined according to the desired vulcanization speed and crosslink density, but is usually 0.3 to 10 parts by mass, preferably 0.5 to 7 parts by mass, per 100 parts by mass of the polymer.

There are no particular restrictions on the type of vulcanization accelerator, and any commonly used accelerator can be used. Examples of the vulcanization accelerator include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and N-cyclohexyl-2-benzothiazyl sulfenamide; thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazole sulfenamide, N-t-butyl-2-benzothiazolyl sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, and N,N'-diisopropyl-2-benzothiazole sulfenamide; and guanidine-based vulcanization accelerators such as diphenyl guanidine, di-orthotolyl guanidine, and orthotolyl biguanidine. These may be used alone or in combination of two or more. Among them, sulfenamide-based vulcanization accelerators and guanidine-based vulcanization accelerators are preferred.

In addition to the above components, the polymer composition may contain appropriate additives, such as release agents and pigments, that are commonly used in the application field.

When the polymer composition is a rubber composition, a known method can be used for its production. For example, the components described above can be mixed using a rubber mixer such as an open roll or a Banbury mixer, and then vulcanized.

As for the kneading conditions, in the base kneading process where additives other than the vulcanizing agent and vulcanization accelerator are kneaded, the kneading temperature is usually 50 to 200°C, preferably 80 to 190°C, and the kneading time is usually 30 seconds to 30 minutes, preferably 1 minute to 30 minutes. In the finish kneading process where the vulcanizing agent and vulcanization accelerator are kneaded, the kneading temperature is usually 100°C or less, preferably room temperature to 80°C. Furthermore, the composition kneaded with the vulcanizing agent and vulcanization accelerator is usually subjected to a vulcanization treatment such as press vulcanization. The vulcanization temperature is usually 120 to 200°C, preferably 140 to 180°C.

When the polymer composition is a resin composition, a known method can be used as the manufacturing method thereof, for example, a method in which the above-mentioned components are kneaded using an extruder (such as a twin-screw extruder) and molded.

As mentioned above, the polymer composition is resistant to shocks and vibrations perpendicular to the orientation direction, and can therefore be used in a variety of applications, including components that are long in one direction, such as automobile bodies, aircraft wings, wind turbines for wind power generation, and sports equipment such as golf clubs. In addition, ring-shaped components such as tires can also be considered components that are long in one direction (circumferential direction), and can therefore be suitably used.

When the polymer composition is applied to a tire, the tire is manufactured by a conventional method using the polymer composition. That is, the polymer composition, which is mixed with various materials as necessary, is extruded to match the shape of the tire components while still unvulcanized, and molded together with other tire components in a tire building machine by a conventional method to form an unvulcanized tire, which is then heated and pressurized in the vulcanizer to manufacture a tire (e.g., a pneumatic tire).

When the above polymer composition is used in tires, it can be applied to various tire components, such as treads (cap treads), base treads, under treads, sidewalls, clinch apexes, bead apexes, breaker cushion rubber, carcass cord covering rubber, insulation, chafers, inner liners, and the like, as well as side reinforcing layers of run-flat tires. In particular, it has excellent impact resistance, durability, and the like, and is therefore suitable for use in treads, sidewalls, and the like.

The above pneumatic tires can be suitably used as passenger car tires, large passenger car tires, large SUV tires, heavy load tires such as trucks and buses, light truck tires, motorcycle tires, run-flat tires, and racing tires. They are particularly suitable for use as passenger car tires.

The present invention will be specifically explained based on examples, but the present invention is not limited to these.

Various chemicals used in the examples and comparative examples will be collectively described below.
Microfibrillated plant fiber: Biomass nanofiber manufactured by Sugino Machine Co., Ltd. (product name: "BiNFi-s Cellulose", solid content 2% by mass, moisture 98% by mass, average fiber diameter 10 to 50 nm, average fiber length 2 to 5 μm)
Oil: soybean oil manufactured by Nisshin Oillio Co., Ltd. (The properties are shown in Table 1. The fatty acid content in Table 1 means the content (mass%) of each fatty acid in 100 mass% of the constituent fatty acids.)
Organic acid amine 1: Carboxylic acid amine salt (FX600 manufactured by Elementis)
Organic acid amine 2: fatty acid amine salt (Kireslite WR-6, manufactured by Chelest Co., Ltd.)
NR latex: Field latex obtained from Muhibbah LATEKS was used. SBR latex: LX110 (E-SBR, vinyl content 18% by mass, styrene content 37.5% by mass, concentration of rubber component in rubber latex 40.5% by mass) manufactured by Zeon Corporation.
NR: TSR20
SBR: Commercially available product manufactured by Zeon Corporation (S-SBR, styrene content 41% by mass)
Carbon black: ^Diablack N550 ( _N2SA41m2 /g) manufactured by Mitsubishi Chemical Corporation
Anti-aging agent: Nocrac 6C manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
Zinc oxide: Zinc oxide type 2 manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Tsubaki sulfur manufactured by NOF Corp. Seimi sulfur manufactured by Nippon Kanretsu Kogyo Co., Ltd. Vulcanization accelerator: Noccela NS manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
Thermoplastic resin: Hybrar 7311F manufactured by Kuraray Co., Ltd.
(Resin name, etc.)

<Preparation of mixed solution>
1,000 g of pure water was added to 500 g of microfibrillated plant fiber to prepare a 0.5 mass % (solid content concentration) suspension of microfibrillated plant fiber, and the suspension was stirred for approximately 5 minutes using a high-speed homogenizer (IKA Japan's "T50", rotation speed: 8,000 rpm) to prepare a uniform aqueous dispersion.
According to the formulation in Table 2, oil, the aqueous dispersion prepared above (calculated as the dry mass (solids content) of microfibrillated plant fiber), and organic acid amines 1 and 2 were mixed, and 100 parts by mass of toluene was further added per 100 parts by mass of oil and mixed. A small amount of hydrochloric acid was added to the resulting mixture, and the mixture was heated to 80°C to perform azeotropic distillation to remove water. The mixture after the water removal was stirred and mixed at 50°C for 5 minutes using a high-speed homogenizer (IKA Japan "T50", rotation speed: 8000 rpm) to prepare mixed solutions 1 to 3.

<Preparation of rubber/microfibrillated plant fiber composite (wet masterbatch)>
According to the compounding recipe in Table 3, a rubber/microfibrillated plant fiber composite was produced.
Specifically, the aqueous dispersion (aqueous dispersion of microfibrillated plant fiber), NR latex (converted into rubber (solid content)), or SBR latex (converted into rubber (solid content)) prepared above was stirred at room temperature for 5 minutes using a high-speed homogenizer to obtain a compounded latex with a pH of 10.2. Next, a 2% by mass aqueous solution of formic acid was added at room temperature to adjust the pH to 3 to 4, and a coagulum was obtained. The obtained coagulum was filtered and dried to obtain rubber/microfibrillated plant fiber composites (WB1, 2).

[Examples and Comparative Examples]
<Preparation of rubber samples>
According to the compounding recipes shown in Tables 4 and 5, materials other than sulfur and vulcanization accelerator were kneaded for 4 minutes at 150°C using a 1.7 L Banbury mixer. Next, sulfur and vulcanization accelerator were added to the kneaded mixture obtained using an open roll, and the mixture was kneaded for 4 minutes at 80°C to obtain an unvulcanized rubber composition. The unvulcanized rubber composition obtained was press molded (vulcanized) at 170°C for 20 minutes to prepare a rubber sample (vulcanized rubber composition).

<Preparation of Resin Composition>
According to the compounding recipe shown in Table 6, the materials were kneaded and molded in a twin-screw extruder to obtain a resin composition (test piece).

<Evaluation items and test methods>
The following physical property measurements and evaluations were carried out on test pieces (vulcanized rubber compositions) taken from the rubber samples produced in the preparation of the rubber samples and test pieces taken from the resin compositions produced in the preparation of the resin compositions. The results are shown in Tables 4 to 6. The reference comparative examples in Tables 4, 5, and 6 are Comparative Examples 1-1, 2-1, and 3-1, respectively.

(Viscoelasticity test)
Test pieces (size: length 20 mm, width 3 mm, thickness 2 mm) taken in the extrusion direction and in the direction perpendicular to the extrusion direction were used, and the complex modulus of elasticity E*a (MPa) in the extrusion direction and the complex modulus of elasticity E*b (MPa) in the direction perpendicular to the extrusion direction were measured using a GABO Iplexer under the conditions of a temperature of 70° C., a frequency of 10 Hz, an initial strain of 10%, and a dynamic strain of 1%.

(Tensile test)
Tensile tests were conducted using No. 7 dumbbell samples in accordance with JIS K6251:2017 "Vulcanized rubber and thermoplastic rubber -- Determination of tensile properties" (standard test temperature (23 ± 2°C)), and the breaking stress TBa (MPa) when elongated in the extrusion direction and the stress FBa (MPa) at 50% elongation of the breaking elongation when elongated in the extrusion direction were measured.

(Impact resistance (Impact strength/Izod impact test))
For each rubber sample (test piece) and each resin composition (test piece), an Izod impact test was performed using an Izod impact tester (manufactured by Toyo Seiki Seisakusho Co., Ltd.) (impact input in a direction perpendicular to the orientation direction of the microfibrillated vegetable fiber (direction perpendicular to the extrusion direction)). A notch with a depth of 2 mm was inserted in the center of the test piece. In the 5.5J-R test, a 5.5J hammer was used to strike the side opposite the notch, causing a crack to develop from the molded product surface without the notch, and the impact strength at that time was calculated. The standard comparative example was set to 100, and each test piece was displayed with an index. The higher the index, the greater the impact resistance (impact strength).

(low fuel consumption)
For each rubber sample (vulcanized rubber composition), the loss tangent (tan δ) was measured using an Iplexer manufactured by GABO under conditions of a temperature of 70°C, a frequency of 10 Hz, an initial strain of 10%, and a dynamic strain of 1%, and expressed as an index (elongation deformation in the orientation direction (extrusion direction) of the microfibrillated plant fiber) with the reference comparative example taken as 100. The higher the index, the better the fuel economy.

(Flex crack growth resistance test)
Using each rubber sample (vulcanized rubber composition) and each resin composition, each test piece was prepared based on JIS K6260 "Vulcanized rubber and thermoplastic rubber - Dematcia flex crack test method", and a flex crack growth test was performed. The rubber sheet was bent by repeating 70% elongation 1 million times, and the length of the crack that occurred was measured (bent in a direction perpendicular to the orientation direction of the microfibrillated plant fiber (direction perpendicular to the extrusion direction)). The reciprocal of the measured value (length) of the reference comparative example was set to 100 and expressed as an index. The larger the index, the more the crack growth was suppressed and the better the flex crack growth resistance.

(Vibration performance)
The vibration performance of each rubber sample (vulcanized rubber composition) and each resin composition was evaluated in accordance with JIS K7391 3.3 central vibration method. The vibration performance of the reference comparative example was set to 100 and expressed as an index. The larger the index, the better the vibration performance.

(Flexural modulus)
Each resin composition (test piece) was kept in a moisture-proof container at 23°C ± 2°C for 24 hours or more. After removing the test piece from the moisture-proof container, the flexural modulus (MPa) was measured immediately (within 15 minutes) according to ISO178 (the flexural modulus in the direction perpendicular to the orientation direction of the microfibrillated plant fibers (the direction perpendicular to the extrusion direction) was measured). The measurement was performed at a temperature of 23°C and a humidity of 50% RH. The standard comparative example was set to 100, and each test piece was expressed by an index. The higher the index, the higher the flexural modulus.

(Bending strength)
The bending strength (kgf/ ^mm2 ) of each resin composition (test piece) was measured using a test method in accordance with JIS Z 2248 (bending strength was measured in a direction perpendicular to the orientation direction of the microfibrillated plant fibers (direction perpendicular to the extrusion direction)). That is, a three-point bending method was used, with a span distance of 200 mm, two supports circular with a radius of 5 mm, and an intermediate push fitting with a semicircular cross section with a radius of 5 mm. The test piece was placed with the reinforced surface facing down, and the crosshead speed was 2 mm/min. The reference comparative example was assigned a value of 100, and each test piece was displayed with an index. The higher the index, the higher the bending strength.

From Tables 4 and 5, the rubber compositions of the examples that satisfy the two formulas E*a/E*b≧1.3 and TBa/FBa≧2.6 have good orientation and dispersion of microfibrillated vegetable fibers, and are excellent in overall performance (the sum of the indices of impact resistance, fuel economy, and flex crack growth resistance) in terms of impact resistance, fuel economy, and flex crack growth resistance. They also have good vibration performance.

From Table 6, it can be seen that the resin compositions of the examples that satisfy the above formula 2 have good orientation and dispersibility of the microfibrillated plant fibers, and are excellent in overall performance (the sum of the indices of impact resistance, flexural modulus, flexural strength, and flexural crack growth resistance) in terms of impact resistance, flexural modulus, flexural strength, and flexural crack growth resistance. They also have good vibration performance.

Claims (13)

polymers, microfibrillated plant fibers and plant oils,
The polymer composition has a ratio (E*a/E*b) of a complex elastic modulus E*a (MPa) in the extrusion direction to a complex elastic modulus E*b (MPa) in a direction perpendicular to the extrusion direction, which satisfies the following formula (1); and a ratio (TBa/FBa) of a breaking stress TBa (MPa) when elongated in the extrusion direction to a stress FBa (MPa) at 50% elongation of the elongation at break when elongated in the extrusion direction, which satisfies the following formula (2).
E*a/E*b≧1.3 (1)
TBa/FBa≧2.6 (2) The polymer composition according to claim 1, wherein E*a/E*b≧1.5 is satisfied. The polymer composition according to claim 1, wherein E*a/E*b≧2.0 is satisfied. The polymer composition according to any one of claims 1 to 3, wherein TBa/FBa≧3.0 is satisfied. The polymer composition according to any one of claims 1 to 3, which satisfies TBa/FBa≧3.4. The polymer composition according to any one of claims 1 to 5, comprising 0.5 to 30 parts by mass of the microfibrillated plant fiber per 100 parts by mass of the polymer. The polymer composition according to any one of claims 1 to 6, wherein the average aspect ratio of the microfibrillated plant fibers in the polymer composition is 10 to 1000. The polymer composition according to any one of claims 1 to 7, wherein the average fiber diameter of the microfibrillated plant fibers in the polymer composition is 10 μm or less. The polymer composition according to any one of claims 1 to 8, which contains a mixed liquid containing an oil containing the vegetable oil and an organic acid amine. The polymer composition according to any one of claims 1 to 9, comprising 0.5 to 30 parts by mass of oil per 100 parts by mass of the polymer. The polymer composition according to any one of claims 1 to 10, which contains 0.1 to 50 parts by mass of an organic acid amine per 100 parts by mass of the microfibrillated plant fiber. The polymer composition according to any one of claims 1 to 11, comprising 0.5 to 30 parts by mass of the microfibrillated plant fiber and 0.5 to 30 parts by mass of the plant oil per 100 parts by mass of the polymer. The polymer composition according to any one of claims 1 to 11, comprising 0.5 to 30 parts by mass of the microfibrillated plant fiber and 0.5 to 30 parts by mass of oil relative to 100 parts by mass of the polymer.